1. Field of the Invention
This invention relates to a technical field of a fiber laser modulation method for modulating the input light to an amplifying optical fiber to output the predetermined output light, a fiber laser modulator.
2. Description of the Related Art
Recently, laser light (pulsed light) is applied to a variety of fields, for example a optical communication field where a pulsed light is used as a signal, and a processing field where the pulsed light is irradiated to an object. And as a laser light generating means, for example a generating means using a YAG laser which is employed in a laser marking device is conventionally known.
The laser marking device employing the YAG laser and the like has problems in that the size of the device is entirely getting larger and the mainteinability is deteriorated due to complicated optical system. Hence, a fiber laser technique where a rare-earth element doped optical fiber, such as Yb in substitution for YAG laser is used as the amplifying medium, is conventionally disclosed in the patent document 1 (Japanese Patent No. 3411852).
As a method for generating the pulsed light by fiber laser, conventionally rectangular input signals are input to the predetermined pump light source to generate pump light, and then the pump light is input to the predetermined amplifying medium to produce pulsed light. In this case, surge pulse was generated in the produced pulsed light on pulse rise time.
In order to use the pulsed light for such as the light source of the display, pulsed light having the rectangular waveform not following the surge pulse is required. Also, not only the light source for display, but also for example the light source of various analyzing devices, the rectangular pulsed light not following the surge pulse is required.
However, in the conventional pulsed light producing method using the fiber laser, the rectangular pulsed light not following the surge pulse could not be produced. Therefore, using the laser light as the light source for the display is very difficult, which limits the applicable scope of the laser light.
In order to use the laser light as the light source for the display, three primary colors, red, blue and green laser lights are required. Of these, each semiconductor laser for irradiating red and blue has been in practical use, but the semiconductor laser for irradiating green has not been implemented the practical use.
Although a light source capable of producing green light in place of the semiconductor laser is strongly desired, the use of the amplifying optical fiber couldn't produce the rectangular pulsed light not following the surge pulse as described above.